The absorption of sugars and electrolytes across the mucosal epithelium is one of the major functions of the intestine. This process is complicated by the fact that these substances must be transported across at least two barriers in series, the membranes at the apical and basal sides of the cells. These membranes may have distinctly different permeability properties. Although considerable experimental work has been done to clarify the mechanism of transcellular transport, there is little direct information on the properties of the individual barriers and their contributions to the overall transport of sugars and electrolytes. The broad aims of this research proposal are to develop a better understanding of the events occurring at these two barriers and also the overall energy requirement for this transport. A number of approaches will be used to realize these aims. First, sugar and electrolyte fluxes will be measured across the mucosal barrier of the epithelial cell of the jejunum and these results compared to results previously obtained in the ileum to determine whether the entry step is qualitatively the same. Second, similar flux measurements will be made on intestine from animals made diabetic to determine what parameters of sugar transport have been altered in this disease state. Third, the electrical properties of the two barriers of the mucosal cell will be measured to further characterize these membranes. Finally, the oxygen consumption of the entire mucosal epithelium will be determined under various conditions of transport, i.e., normal and diabetic, to determine the overall energy requirements of sugar and electrolyte transport. A knowledge of these fluxes, the electrical properties of the membranes and the oxygen requirements of the tissue will greatly enhance our understanding of sugar and electrolyte absorption and will make it possible to relate this knowledge to disease states of electrolyte and carbohydrate absorption.